Draw carriage for drawbench



Nov. 25, 1958 c 2,861,679

DRAW CARRIAGE FOR DRAWBENCH Filed April 5, 1956 4 Sheets-Sheet 1 Fig.l

INVENTOR George A.Mi1chell ATTORNEY Nov. 25, 1958 G. A. MITCHELL 2,361,679

DRAW CARRIAGE FOR DRAWBENCH Filed April 5, 1956 v 4 Sheets-Sheet 2 Nov. 25, 1958 G. A. MITCHELL DRAW CARRIAGE FOR DRAWBENCH 4 Sheets-Sheet 5 Filed April 5, 1956 Fig.5

United States PatenrO 'ice 2,861,679 DRAW CARRIAGE "FOR RAWBENCH George A. Mitchell,Hubbard,i0hio, assignor to Lombard Corporation, Youngstown, Ohio, a corporation of Ghio Application April 3, 1956, Serial No. 575,750

6-Claims. c1. 205-3 This invention relates to drawbenches adapted to draw tubes and the like through a'die andmore particularly to a draw carriage for such apparatus capable of performing'a plurality of simultaneous drawing operations.

As is well known to those skilled in the art, a drawbench employs, as a basic component, a circular die through which a tube is drawn in order to elongate the tube and reduce its diameter. In the drawing operation an end of a' tube to be drawn ispassed through the die and engaged by gripper jaws carried on a draw carriage or dolly which travels on a track extending parallel to the central axis of the die. This draw carriage engages one or more continuously moving chains which force it along its track outwardly and" away from the die, thereby pulling the tube through the die.

In order to increase the production output of a drawbench, a plurality 'of tubes are simultaneously drawn through a corresponding number of spaced dies during one drawing operation. It is a common occurrence in the drawing of these tubes for the same to jump forwardly with considerable force as the trailing ends thereof pass through the dies, the obvious reason beingthat the tubes are under substantial tension during the drawing operation and the sudden release of such tension is accompanied by a release of energy which propels the tubes forwardly. This is a serious problem in that the forward ends of the tubes are driven against the draw carriage so that often they are buckled and rendered'unsuitable for a subsequent drawing operation, or partially so.

Another problem arises during a multiple drawing operation due to the fact that the various tubes whichare drawn simultaneously are not of equal length, and consequently, leave their respective dies at different times. The resultant release of energy by the tubes which first leave the dies while other tubes are still in tension skews or twists the draw carriage in its travel along the aforesaid track. Consequently, it becomes necessary'to provide some sort of lateral support for the draw carriage. This may be done conveniently by a pair of vertical guideways extending parallel with the track together with some sort of rigid guiding members, such as bronze'liners,'interposed between the carriage and the vertical guideways.

The necessary lateral support for the draw carriage has been provided for in prior drawbenches employing a single draw chain by forming the track forthe carriage from a single integral steel column and by machining vertical guideways in the sides of this column. With this arrangement, it is possible to obtain fine tolerances between the guiding members on the draw carriage and the machined guideways so that constant and substantially even lateral support for the carriage is maintained throughout the length, of the track.

A single draw chain bench employing an integral column has certain disadvantages in that itis diflicult to conveniently discharge-"the 'n'ewly drawntubes directly beneath the carriage. This results from the factthat the single chain is located directly below the carriage. To circumvent this problem, drawbencheshave been pro- 2,861,679 Patented Nov. 25, 1958 posed in which twodraw chains are employed'on either side of the central axis of the draw carriage to facilitate discharge of the tubes from-beneath the carriage. This type of arrangement requires a drawbench frame in which one of the two tracks for the draw carriage is carried on a cantilever beam arrangement.

In constucting a'trackfor'a drawbench employing a cantilever beam arrangement, it is considered most convenient and economical 'touse welded steel construction. With this type of construction, however, the fine tolerances a'chieved'with the use of an integral column are unattain- It is,'acco rdingly, an object of this invention to provide:

means which will afiord constant and substantially even: lateral'support for a draw carriage throughout its path of travel regardless of variationsin the lateral support-- ing rails forthe draw carriage, such as those which in-- herently exist in a draw carriage'of welded steel construction. v

A further obejct of 'theinventio'n lies in the provisionof suitable lateral supporting members for a draw carriage which will withstand the terrific lateral forces resulting at the end of a simultaneous draw of a plurality of tubes when the tubes of various lengths leave their respective gripper jaws are forced into' gripping position by airdies at different times. In accordance with this object the present invention provides rollers mounted on pistons which reciprocate in bores machined in the opposite ends of each side of the'dra'w carriage lying adjacent one of the said vertical rails. Interposed between each piston and its associated bore is a .pre-loaded hydraulic shock absorber. In this manner lateral forces produced on the draw carriage are'eifectively dissipated by theshock absorbers and are prevented from damaging the rollers and their associated parts which would otherwise be damaged without the provision of some type of shock absorbing means.

A still further object of the invention is toprovide means in a draw carriage for absorbing the kinetic energy of'newly drawn tubes in a manner to prevent damage to the tubes and gripper jaw mechanism as a result of their being propelled against the draw carriage at the conclusion of a drawing operation. More specifically, this further object of the invention resides in the provision of a simple mechanism which'serves both to absorb the kinetic energy of newly drawn tubes and to operate the gripper jaws which engage the forward ends of the tubes during a drawing operation. In accordance with this object the present invention provides a pneumatically operated piston located behind the gripper jaws of the draw'carriage for moving the same from retracted to gripping position. Located directly behind the piston is a pre-loaded hydraulic shockabsorber. At the beginning of a draw the pressure acting on the piston; and at the completion of a draw the gripper jaws and piston are forced back against The kinetic energy of the tube tion will become apparent 'fromlthe' following detailed description taken in connection with the accompanyingdrawings whichform a part of this specification and in.

which Figure 1 is a side elevation of a drawbench assembly with which the present invention may be used;

Fig. 2 is a top view of the apparatus shown in Fig. 1; P Fig. 3 is a sectional view taken along line IIIIII of Fig. 4 is a sectional view of the die block of the drawbench shownin Figs. 1 and 2;

Fig. 5 is a top View of the draw carriage of the present invention;

Figs. 6 is a sectional view taken along line VI-VI of Fig.

Fig.7 is a sectional view taken along line VIIVII of Fig. 5; and

Fig. 8 is a cross sectional view of the pre-loaded hydraulic shock absorbers used in the invention.

Referring to Figures 1-3, the numeral 10 represents generally the main framework of a drawbench assembly which is comprised of a plurality of spaced frame sections 12, as shown in Fig. 3. The frame sections 12 may be fabricated of ordinary structural members Welded or otherwise securely fastened together. Each section includes an upright member 14 and a horizontally disposed cantilever beam 16 extending outwardly from the upright member or post 14. Depending downwardly from the outer end of the cantilever beam 16 is a short beam section 18, which carries at its lower end a track support 20. The support 20 is one of a complementary pair, a second support 22 being carried by the post 14, as shown.

As will be understood, the complete drawbench assembly incorporates a plurality of frame sections 12, mounted in spaced relation along the length of the drawbench. Carried by the supports 20 and 22 of such sec tions are spaced tracks 24 and 26 which may, for example, be elongated sections of angle iron. The tracks 24 and 26 support a draw carriage 28 against gravity and guide it in longitudinal movement throughout the length of the drawbench, as will be subsequently developed herein. Adjacent and slightly below each of the tracks 24 and 26 are guiding and supporting channels 30 and 32 for a pair of spaced draw chains 34 and 36 which are employed to draw the carriage 28 along the tracks 24 and 26 during a drawing operation. Supported in depending relation from the cantilever member 16 is another channel 38 which supports and guides a third chain 40 which is utilized in the illustrated apparatus as a return chain for returning the carriage 28 to its initial position immediately following a drawing operation.

In accordance with preferred practice, the main draw chains 34 and 36 are endless and rotate continuously in one direction. Therefore, suitable sprocket wheels 42 are provided at each end of the respective traverses of the chains 34 and 36, and additional guiding and supporting channels 30' and 32 (Figure 3) are supported on the lower portions of sections 12 so that the lower or return reaches of the drive chains may be properly supported.

At the right-hand end of the drawbench assembly there is provided a heavy duty drive motor 44 and gear reducer 46, the latter of which has driving connection with the chains 34 and 36 for effecting synchronous movement thereof in the manner'desired. In the illustrated embodiment there is also provided a smaller drive motor 48 having driving connection with the return chain 48. The motor 48 is preferably energized only upon completion of a drawing operation, being maintained in an inoperative condition throughout the duration of an actual drawing operation.

At the left end of the main frame 10 of the drawbench is a die block 50, shown in detail in Figure 4. The die block comprises a main shank portion having a plurality of spaced die assemblies extending therethrough. Each die assembly comprises a die cup 52 having a generally spherical end which fits into a cooperating cup formed in die block 50. The die 53 is carried within the die 4 cup 52 and is held therein by a die cup nut 55, substantially as shown. In the drawing operation, a plurality of tubes 57 are drawn through these dies by the draw carriage 28.

Extending to the left of the die block 50 is an elongated mandrel supporting table 54 which has means 56 at its extreme left end for anchoring and manipulating a plurality of mandrel rods 58 corresponding in number to the number of dies 53. Each of the mandrel rods has an enlarged head at its extreme right end which is inserted into a corresponding die during a drawing operation.

In conventional tube drawing practice, a plurality of tube blanks are first passed over the plurality of mandrel rods 58, which are then inserted into the openings in the dies 53. The leading ends of the blanks are gripped by the draw carriage 28 which, when moved away from the die block 50, carries the tube blanks along with it. The blanks are thereby reduced to the dimensions of the annular opening between the inner periphery of a die and the outer periphery of the enlarged head of the mandrel which extends into the die.

To facilitate loading of the tube blanks onto the mandrel rods 58, there is provided above the main frame 10 a rack or platform 60 which supports a plurality of blanks, not shown, arranged generally in end-to-end relationship with respect to the rods 58. Suitable means, not shown, are provided for elevating the enlarged ends of the mandrel rods and for sliding the blanks over these enlarged ends during a loading operation. An operators platform 62 is provided adjacent the die block 50.

Referring to Figs. 5-7, the draw carriage of the present invention comprises a rigid frame 64 including rigid side members 66. The draw carriage is provided with four supporting wheels or rollers 68 to facilitate horizontal movement and four guiding wheels 70 rotating about vertical axes. The wheels 68 and 70 are adapted to engage the horizontal and vertical surfaces, respectively, of the guiding and supporting tracks'24 and 26 whereby the carriage 28 may have free guided movement throughout the length of the main frame 10 of the drawbench.

At the bottom of the rigid side members 66 shown in Fig. 5 are machined a pair of keys 72 and 74 whichfit into cooperating keyways in a gripper head 76. The gripper head comprises a heavy block of steel having formed therein a plurality of forwardly converging guide slots 78 adapted for the reception of stock-engaging grip bits 80 and 82, the arrangement being such that upon forward movement of the bits the same are caused to converge while upon rearward movement they are caused to diverge. The guide slots 78 are open at the lower side of the gripper head 76, there being a plurality of spaced plates 84 (Fig. 6) provided to partially enclose the openings .thus formed and retain the grip bits 80 and 82 therein. Each of the bits 80 and 82 is provided with a transverse slot 86 in its upper surface for the reception of transverse arm portions of a slide block 88 which is guided for longitudinal movement on the spaced plates 84. Upon forward movement, for example, of the slide block 88, its associated grip bits will be caused to converge.

To actuate each of the slide blocks, there is provided an arrangement including longitudinally movable pistons or plungers 90 having enlarged heads 92 which engage cooperating slots in the slide block 88. The pistons 99 are received for reciprocating movement within bores or cylinders 94 carried by a metal transversely-extending block 95. Spring clips 96 normally retain the pistons 90 in retracted position. A transversely extending passage 98 is provided in the block for conducting compressed air into the respective cylinders 94. Upon the introduction of compressed air into cylinders 94, pistons 90 willbe forced to the left as shown in Fig. 6, thereby causing the grip bits 80 and 82 associated with each piston to converge.

At the extreme right end of the cylinders 94 is placed a pre-loaded hydraulic Hydra Sprin'g' (trademark) shock absorber 100, hereinafter more fully described. An impact on plunger 110 of shock absorber 100 will compress the fluid contained within the shock absorber to thereby absorb the kinetic energy of -a moving object. Upon the completion of a draw, the tube blanks engaged by grip bit 80 and 82 will force slide blocks 88 and pistons 90 back against the plungers 110 of shock absorbers 100 which dissipate the forward kinetic energy of the blanks and slide block assemblies. In the retracting troke grip bits 80 and 82 diverge and allow the blanks to drop out through the lower openings of the guide slots 78.

In order to effectively carry out drawing operations in the manner described above, it is necessary that the area below the draw carriage 28 be open so that upon discharge of the drawn tubes from the lower side of the carriage the tubes may fall freely into -a receiving bin or the like. It has been found-most practical to drive the draw carriage from opposite sides, leaving the bottom area entirely clear. Accordingly, the drive chains 34 and 36 are positioned immediately below and adjacent the side edges of the carriage 28, as shown in Figs. 1 and 2.

To engage thecarriage 28 with the chains 34 and 36 for effecting a drawing operation there is provided a pair of retractable, chain-engaging hooks 120 which are mounted at opposite sides of the carriage 28. The hooks 120 are normally urgedupwardly into a'retracted position; while air-operated plunger assemblies, not shown, carried within the housings 122 are'adapted to move the hooks downwardly into an extended or chain-engaging position. It is to be understood, of course, that the drive chains 34 and 36 are driven continuously and synchronously in the same direction. However, various factors may operate to cause the chains to move slightly out of phase with respect to each other. As'will be readily understood, any tendency of the drive chains to move in an out-of-phase relationship will cause an unbalanced drawing load to be applied to the carriage unless the hooks themselves can be adjusted to compensate for such unbalance.

In order to prevent a condition of unbalance, the hooks 120 are mounted on slidable block assemblies 124 and 126 which are received in slots 128 in the carriage side members 66 and adapted for limited longitudinal sliding movement with respect thereto. An equalizer or draw bar 130 is mounted for pivotalmovement about a centrally located vertical axis 132. As shown in Fig. 5, the forwardly extending portions 130 of the draw bar are positioned outwardly with respect-to the side members 66 and are adapted to abut-the rear end faces of the hook mounting a semblies 124 and 126. Normally the assemblies 124 and 126 are drawn back against the draw bar 136 by means of suitable springs 131 and 133. When the hooks 120 are forced downward to engage the draw chains 34 and 36, and one hook engages before the other, the first-engaged hook will begin to move relative to the carriage; and as it does o it will cause the draw bar 130 to pivot about its axis 132, moving the other hook in the opposite direction relative to the carriage until such hook finally-engages its associated drive chain. At this time both hook assemblies-124 and 126 are drawn tightly against the draw bar. -Drawing forces are in this manner transmitted through the bar to the carriage. Thus, any out-of-phase relationship'of the draw chains 34 and 36 is compensated for by relative longitudinal movement between the hook assemblies 124 and 126; and, consequently, unbalanced forces and other undesirable efiects are wholly avoided.

At the completion of a drawing operation, some of the blanks will leave their associated dies before others. The sudden release of energy by the blanks which first leave the dies while other blanks are still in tension tends 6 to twist or skew the draw carriage 28 with respect to tracks 24 and 26. In order to prevent damage to the draw-carriage due to the terrific transverse impact forces resulting from the twisting action described above, the arrangement, best shown in'Fig. 7, was devised.

As shown in Figs. 6 and 7 the rigid side members 66 have bores 134 machinedin the opposite extremities of their outwardly facing, long transverse sides. Within each of the bores 134 is inserted a cylinder'liner 136 which carries, for reciprocating movement, a plunger member 138. The plunger member carries one of the guiding wheels 70 which is rotatably supported on a vertical pin 140. Within the-portion of plunger member 138 extending into cylinder liner 136 is a cylindrical chamber which carries a pre-loaded hydraulic shock absorber 142. The shock absorber is bottomed within its associated cylindrical chamber and has an elongated plunger 144 extending into a threaded bore which receives an adjusting screw 146.

As shown in Fig. 8, the shock absorber 142 comprises an outer cylinder assembly 148 closed at one end except for a small threaded opening 150 therein. The other end of the cylinder 148' is fitted with an annular member 152 having an elongated, centrally disposed neck portion which defines a smaller inner cylinder 154. Within the cylinder 154 is a reciprocable piston 156 which carries the elongated plunger 144. Leakage around the plunger is prevented by a seal 158. Within opening 15!! is received a set screw 162. A seal 164 surrounding a plunger 165 completes the assembly. Suitable oil or other liquid completely fills the space enclosed by cylinder 148 and member 152. The arrangement is such that by adjustment of setscrew 162, a shock absorber of this type can be pre-loaded in the range of 600 pounds.

In order thatplunger member 138 may reciprocate within cylinder liner 136, an annular spacing D must be provided between the left end of cylinder liner 136, as shown in Fig. 7, and ashoulder 137 formed on the plunger. It is necessary that the rollers 70 never lose contact with the vertical portion of tracks 24 or 26. Otherwise, chattering or knocking will result between the draw carriage and the vertical portions of tracks 24 and 26. To insure that rollers 70 will always be in contact with their associated rails, the adjusting screw 146 for each guide wheel assembly is tightened so that its advances a distance equal to the distanceD and compresses the shock absorber. Thus, if a lateral impact is such that shoulder 137 is forced against cylinder liner 136 on one side of the draw carriage, the shock absorber on the other side of the carriage will expand by an amount equal to the distance D, and each guide wheel 70 will always be kept in contact with its associated vertical rail. The arrangement is such that firm and substantially even lateral support is continually afliorded the draw carriage by the four guide wheel assemblies positioned at the four corners of the carriage. When the carriage skews or twists due to the release of energy by part of the tube blanks while other blanks are still in tension, the hydraulic shock absorber 142 will cushion the resulting lateral impact on the vertical'portions of track 24 and 26. Since the compressibility of the oil within cylinder 148 is very low, plunger 144 will spring back to its original position instantaneously after an impact is applied to the shock absorber. Thus, firm and continuous lateral support of the carriage is combined with the ability to absorb impact loads. I

The shock absorbers 100 associated with pistons 90 are similar to that shown in Fig. 8except that a check valve, not shown, is provided within cylinder 148 .to dampen the return stroke of plunger 144 after an impact is applied following the completion of a draw. In this manner the tendency of the plunger 144 to recoil is minimized following the application of an impact load.

In operation, a plurality of tube blanks or workpieces are first loaded onto the mandrel rods 58, and swaged drawing operation.

or reduced diameter ends of the workpieces are inserted through the die openings. Next, the draw carriage 28 is moved up to the die block 50 by return chain 41) which engages a member 148 on the carriage (see Figure During this time, the spring clips 96 retain the grip bits 80 and 82 in their retracted position so that the bits can be easily passed over the reduced diameter portions of the tube blanks extending through dies 53. When the carriage 28 is in its extreme left position shown in Figs. 1 and 2 and the grip bits extend over the reduced diameter portions of the tube blanks, suitable means, not shown, will admit compressed air through passage 98 into cylinders 94, the arrangement being such that pistons 90 and grip bits 80 and 82 will be forced forward into gripping position.

After the grip bits engage the ends of the tube blanks, the hooks 120 are moved downward into a chain-engaging position, and the carriage 28 begins to move to the right as shown in Figs. 1 and 2, thereby initiating the At this time the air pressure on pistons 90 is released. However it will be observed that the application of drawing force by the grip bits 80 and 82 merely tends to draw the same more tightly into engagement with the tube blank so that air pressure is no longer necessary for this purpose. Likewise, when the hooks 120 engage their associated drive chains during a draw, they will remain in chain-engaging position without application of an external force due to frictional forces between the hook and chain.

As the drawing operation is completed and the draw carriage reaches its extreme right position shown in Figs. 1 and 2, the tube blanks will snap free of the dies 53. However, due to the fact that some of the drawn tubes will be longer than others, part of the tubes will snap free while others are still in tension, resulting in terrific lateral impacts on the vertical portions of tracks 24 and 26. These impacts are absorbed by the shock absorbers 142 carried within plungers 138 in the manner described above. As each tube snaps free of its associated die, it forces grip bits 80 and 82 and piston 90 against plunger 110, and then recoils and is ejected through the bottom opening of guide slot 78.

When all of the tube blanks are drawn and the pressure of chains 34 and 36 is removed from hooks 120, they will snap back into retracted position. In the illustrated apparatus there is provided a receiving rack 251) (Fig. 3), extending along the front side of the drawbench frame 10, in which the finished tubes are deposited following a drawing operation. The rack 2519 is positioned in ofiset relation with respect to the draw carriage 28 to facilitate unloading of the finished tubes. A sloping run out tables 252 is located directly below the carriage to receive the tubes as they drop and to direct the same into the receiving rack 250. To return the draw carriage to its initial position the return motor 48 is energized, and the return chain 40 draws the carriage back to the die block 50.

Although the invention has been descibed in connection with a certain specific embodiment, it should be readily apparent to those skilled in the art that various changes in form and arrangement of parts of the apparatus may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In a drawbench adapted to draw tubes and the like through a plurality of dies having their center lines disposed parallel to each other in a common plane, the combination of a pair of substantially L-shaped guideways disposed on one side of said dies and extending parallel to the central axes thereof, one of the legs of each L-shaped guideway lying in a horizontal plane and the other leg of each guideway lying in a vertical plane, a draw carriage, anti-friction members mounted on said draw car riage to effect movement of the draw carriage along the horizontal legs of said guideways, antifriction rollers carried by said draw carriage and interposed between the draw carriage and the vertical legs of said L-shaped guideways, and hydraulic shock absorbers carried by said draw carriage for urging said rollers outwardly against said vertical legs.

2. In a drawbench, a draw carriage adapted to draw tubes and the like through a plurality of dies, said drawcarriage being movable along the central axes of said dies, guideways for restricting transverse movement of said draw carriage with respect to the central axes of said dies, anti-friction members carried by said draw carriage, and shock absorbers urging said anti-friction members against said guideways.

3. The combination claimed in claim 2 wherein the draw carriage is substantially rectangular in cross-section and wherein the anti-friction members are four in number, the anti-friction members being disposed at the opposite ends of the long transverse sides of said draw carriage.

4. The combination claimed in claim 2 wherein the shock absorbers are of the pre-loaded hydraulic type.

5. In a drawbench, a draw carriage substantially rectangular in shape for drawing tubes and the like through a plurality of dies, said draw carriage being movable along the central axes of said dies, elongated guide members extending along two oppositely disposed sides of said draw carriage for restricting transverse movement of the draw carriage with respect to the central axes of said dies, cylindrical bores located in the opposite ends of each of said oppositely disposed sides, piston members reciprocable within said bores, anti-friction elements carried by said piston members and adapted for engagement with said guide members, and shock absorbing means carried by each of said piston members and interposed between the piston members and the draw carriage for urging said piston members and their associated anti-friction members aganist said guide members.

6. In a drawbench, a draw carriage substantially rectangular in shape for drawing tubes and the like through one or more dies, said draw carriage being movable along the central axes of said dies, elongated guide members extending along two oppositely disposed sides of said draw carriage for restricting transverse movement of the draw carriage with respect to the central axes of said dies, openings located in the opposite endsof said oppositely disposed sides, piston members reciprocable within said openings, and shock absorbing means interposed between said piston members and said draw carriage for urging the piston members against said guide members.

References Cited in the file of this patent UNITED STATES PATENTS 388,782 McCool Aug. 28, 1888 1,911,157 Leech May 23, 1933 2,404,234 Kerr July 16, 1946 2,551,260 Garwig May 1, 1951 2,554,998 McIlvried May 29, 1951 2,731,141 Kerr Jan. 17, 1956 FOREIGN PATENTS 595,471) Great Britain Dec. 5, 1947 

